interface A{
  double f(double x,double y);
}
class B implements A {
public double f(double x,double y){
	return x*y;
}
int g(int a,int b){
	return a+b;
  }
}
public class xiti6_1{
public static void main(String args[]){
	A a=new B();
	System.out.println(a.f(3.0,5.0));
	B b=(B)a;
	System.out.println(b.g(3,5));
  }
}
